The majority of hand-propelled wheelchairs in present use are equipped with tubular steel hand rims of approximately 21 inches in diameter. The cross sectional contour of the hand rim is a circle of approximately 5/8-inch diameter. Each hand rim is mounted outboard of its respective wheel by four tubular spacers (standoffs) to provide a clearance of approximately 3/4 of an inch. While generally suitable for their intended purpose of propelling and maneuvering the wheelchair, the standard hand rim has numerous disadvantages.
The relatively small diameter (5/8 of an inch) of the hand rim tubing section provides only a limited gripping surface for the user. Thus, when the user attempts to propel the chair in difficult situations, as when going up ramps, traveling on soft carpets, or traversing rough terrain, he often experiences difficulty and must resort to such tactics as placing his hands over both tire and hand rim to exert sufficient torque. The limited surface area of the standard hand rim also limits the ability of the user to properly and safely control and brake the wheelchair while descending a ramp. Due to the lack of surface area the user often finds it necessary to wrap his fingers around most of the tube diameter to get a sufficient grip, and thus tends to get his fingers caught up on the standoffs. This problem is particularly acute when the user is descending a ramp.
Even assuming that the user is able to satisfactorily propel and control the wheelchair, and it can probably be assumed that this is the case much of the time, it is clear that mobility can be improved inasmuch as the conventional hand rim does not fit the user's hand in a comfortable manner, especially when extra torque or gripping action must be applied. Thus, a considerable amount of the user's effort is expended in gripping the hand rim rather than in applying torque to propel the wheelchair.
There are on the market some lightweight wheelchairs that are equipped with integral hand rim and wheel rim assemblies. For example, U.S. Pat. No. 2,938,738 discloses a combined hand rim and wheel rim for a wheelchair that is preferably formed from a single extruded section. The hand rim has a non-circular cross-sectional contour. This construction provides a continuous web between the wheel rim and the hand rim, thus avoiding the problem wherein the user's fingers get caught up in the stand offs. However, this configuration has the disadvantage that it limits the grip applicable to the hand rim since the user's fingers cannot fully encircle the hand rim.
In recent years wheelchair sports have become increasingly popular, and have prompted a number of improvements directed toward making wheelchairs more easily and efficiently maneuverable. Sport wheelchairs are often equipped with hand rims formed from a slightly larger diameter tubing which improves the grip to some extent. The grip may be further improved by providing a soft vinyl surface on the hand rim, but this has the disadvatage of considerably diminishing the durability of the hand rim.
A different set of problems is presented for those users with partial quadraplegia and thus limited grip strength. A typical prior art hand rim for such users utilizes a circular ring similar to a regular hand rim, having a plurality of radially or axially projecting handles or push rods which the user may push with his palm without having to grip. These so-called "projection" hand rims are useful when required, but are heavy and relatively expensive. Moreover, they are extremely awkward and unsuitable for general use. The main problem is that the push rods easily becomes caught up on draperies, furniture, and the like. U.S. Pat. No. 4,039,199 discloses a system wherein the push rods are partially retracted towards the bottom of their travel, thus at least partially obviating this problem. However, this result is achieved at the expense of the complexity.